Best easy make ahead finger food appetizers to be served at room temp for large pre-prom party with adults and teens?

Little turnovers. I love using a nice, flaky cream cheese pie dough for mini turnovers. You roll out the dough, cut it into small circles, and fill it with whatever you like (pesto, sun dried tomatoes, and walnuts; goat cheese and caramelized onions; sautéed greens and mushrooms...). Brush with egg wash and bake.

I would avoid anything red that could stain....just picturing the high drama and tears of a girl dropping red pepper sauce all over her white prom dress. Be prepared with some stain remover pens... One bite dishes with minimum mess are the best. Gougeres....these fig and blue cheese savories are great: http://www.food52.com/recipes/8010_fig_and_blue_cheese_savouries
maybe veggies with aoli dipping sauce http://www.food52.com/blog/2070_aioli_two_ways
party mix for grown-ups http://www.food52.com/blog/1167_party_mix_for_grownups

How about tea sandwiches?

I love how easy it can be to put together a great cheese platter with some crackers, dried fruits and nuts, and a chutney or preserve.

You can make a nut mix. These are amazing: http://www.food52.com/recipes/3140_chaat_masala_mixed_nuts

These also look great: http://www.foodnetwork.com/recipes/nigella-lawson/the-union-square-cafes-bar-nuts-recipe/index.html

How about gravlax? You can cure it days in advance and then slice over small slice of brown bread and serve with a mustard vinaigrette

scoop the seeds out of cherry tomatoes with a small mellon baller or other spoon, and fill each one with freshly made olive tapenade. top with chopped chives or a crumble of feta. yum!

I make these fabulous glazed red pepper
fennel almonds that I serve with raw milk manchego cheese & prosciutto wrapped bread sticks. It makes for a beautiful platter and is the perfect combo of sweet, salty & spicy!
http://www.epicurious.com/recipes/food/views/Glazed-Red-Pepper-Fennel-Almonds-107680?mbid=ipapp

For a similar event, I made cheese straws from thawed out puff pastry (found in the freezer section of your grocery store). Roll each piece of puff pastry out a little bit to about 1/4 inch thick. Cut into 3x1/2 inch rectangles with a pizza cutter or sharp large knife.Transfer the pieces to a parchment lined cookie sheet. They can be close together because they will rise but not spread very much. Sprinkle with lots of freshly grated Parmesan or Romano cheese, and a little paprika or garlic salt if you like. Bake at the temp recommended on the package. Easy, peasy! There are never any left overs.

oops, forgot the link! -- http://food52.com/recipes/12802_prosciutto_goat_cheese_stuffed_dates

These are hands-down my favorite appetizers- prosciutto wrapped, goat-cheese stuffed dates.

Mini-sausage mozzarella "kebabs":

You will need:
precooked chicken or pork sausage (like Italian), cut to ~1" pieces.
bocconcini mozzarella, or any fresh mozzarella cut to about the same size as the sausage
thin pretzel sticks
grape tomatoes
basil leaves (optional)

Take preztel and spear a piece of sausage, basil (if using) and a piece of mozz. Alternatively, a piece of cheese, basil, and a tomato.

I've made Martha Stewart's grapes rolled in roquefort or goat cheese and minced nuts. For the teen crowd, I'd do the goat cheese. Mix 8 oz cream cheese with 3 or 4 oz goat, thin with a few TBSP cream so it is pliable. Drop in 40 red or green grapes and mix up gently. Fish out one by one and roll into a round between your palms with a thin coat of cheese over all (very pita but you can do it.) Roll in chopped nuts, anything your like, from mild macademias' to pecans. You might like to roll some in chopped dried cranberries. Chill well (4 hrs to overnight) and these can be set out for quite a few hours at room temp. The is also a similar recipe on this site if you search, but she makes them more rustic. I make perfect rounds and put a sprig of grapes in the corner to hint at what it is.